An Overview of DNA Computing

DNA is used by all life on earth to store genetic information. Because of its double helix structure, it is a very stable molecule. This stability and information-storing ability have inspired the development of a new type of technology: the DNA computer.

The first DNA computer was created in 1994 and was good for only one thing, solving a specific mathematical problem. The more modern DNA computer MAYA-II, developed by scientists at Columbia University and the University of New Mexico, is made of 100 DNA circuits and can play a mean game of tic-tac-toe, though it needs half an hour to make each move. Its usefulness is limited to demonstrating “proof-of-concept,” but DNA computers have amazing potential.

In the computing industry, traditional silicon microchips become smaller and faster at an exponential rate. Moore's Law is the observation that per dollar spent, the computing power of microprocessors doubles about every two years (some sources say every eighteen months). But Moore's law has a dirty little secret: silicon chips have a practical upper limit of speed and power. DNA may be the new material that will take the place of silicon to keep Moore's law going.

There is a slew of practical benefits to using DNA in computer. Since DNA is found in every living cell, it is an incredibly abundant resource, and it requires very little processing to be usable in a computer. Silicon, by contrast, must be extensively refined and purified to be useful. And while traditional computers are manufactured using toxic materials, DNA computers are a clean technology.

Silicon circuits have only two settings, “on” and “off,” which leads to the binary math (ones and zeroes) used by conventional computers. Silicon “on” and “off” settings are electrical in nature, so when the power goes out, all computing ceases. By contrast, DNA has four possible settings (called bases), represented by the letters A, C, G, and T, so DNA computer math is quaternary (base 4). The bases are chemical structures that do not require electricity, and in fact DNA computers can get the energy they need to work from other DNA.

Though DNA may replace silicon in many everyday computers, the most incredible DNA computing applications are medical. In the future, DNA computers may be able to seek out cancer cells, then cure the cancer by releasing a drug to treat it. They may be able to practically cure diabetes by monitoring blood sugar and dispensing insulin as needed.

For many medical applications, DNA computers called “computational genes” would be integrated into the genetic material already in the patients' cells. Computational genes have some of the same DNA markers found in ordinary genes, but instead of coding for protein structure, they will be programmed to react to certain input (such as a DNA sequence associated with cancer) with a certain output (such as a molecule to treat that cancer).

A challenge to the development of computational genes is delivery of the DNA into cells and incorporation into the patients' own DNA. Another is keeping the computational genes from being treated by the immune system as foreign invaders. But research into this technology is moving at breakneck speed, and solutions to these and other problems may be found relatively soon. New medical applications not yet conceived of are likely to appear on the horizon in the near future.

DNA is very small, with its bases spaced every 0.35 nanometers. A DNA computer more powerful than any supercomputer now in existence would theoretically be smaller than a laptop's “on” button. DNA promises multiple revolutions in computing: in size, in power, and in potential applications.